Skip to main content

Jeans, James Hopwood (1877–1946)


James Hopwood Jeans, an English physicist and astronomer was educated at Merchant Taylor's School and Trinity College, Cambridge, where he received high honors in mathematics in 1898. He taught mathematics at Cambridge as university lecturer from 1904 to 1905, at Princeton as professor of applied mathematics from 1905 to 1909, and again at Cambridge as Stokes lecturer from 1909 to 1912. In 1912 he resigned all regular offices to live on a private income and later also on the sale of several popular books. He was honorary secretary of the Royal Society, president of the British Association for the Advancement of Science, and professor of astronomy at the Royal Institution.

Jeans was a man of undoubted ability and originality and early won a deservedly high reputation, being elected a fellow of the Royal Society at the age of twenty-eight. His main contributions to science were in two fields: the kinetic theory of gases, in particular the equipartition of energy and radiation; and cosmogony, in particular the forms of equilibrium of rotating gravitational masses and the kinetic theories of aggregates of stars. The last constitute perhaps his best and most enduring work.

During the early 1930s Jeans wrote a number of highly successful books popularizing science, and these, together with Physics and Philosophy (1942), contain his philosophical writings. His popular expositions of scientific theories are marked by their simplicity of expression and by the striking and illuminating examples and analogies they contain.

Although Jeans contributed nothing substantial to philosophy, his views gained attention because of his eminence in the scientific field and because of their being presented together with expositions of abstruse scientific theories widely agreed to be of philosophical interest. Jeans's writings on philosophy were slight in quantity as well as in quality; even Physics and Philosophy contained only about fifty pages of his own views.

His position was never consistently developed and is therefore unclear. Indeed, he seems almost to have felt that it would be against the spirit of philosophy to argue with rigor, clarity, and decent caution. His work is certainly characterized by loose reasoning, and not infrequently by plainly false or confused premises. Broadly, however, his views were that science must connect observables with observables by means of chains of mathematical equations. He held that mathematical formalization is the prime part of physical knowledge and that interpretative models of this formalism are outdated and confusing crutches in coming to know about the world. This was not because Jeans believed that only propositions about observables have a meaning. He was no positivist, despite his claim to be one. On the ground that physical measurement reveals only relations between instruments (including one's eyes and ears) and reality, he believed in a Lockean substratum that is forever hidden from us. He also held that modern science suggests that there is some room for the operation of free will, but it is unclear why he adopted this opinion. His attitude to the common fallacy that the uncertainty relations of quantum physics establish the possibility of free will is quite ambiguous.

The most striking and most widely discussed of Jeans's conclusions is that reality, the Lockean substratum, is mental, not material. This conclusion reaches its most startling form in the final chapter of The Mysterious Universe, where Jeans argued that the universe consists of the thoughts of a Pure Mathematician, God.

Jeans assertedit is hardly an argumentthat the universe is shown to be rational by the very fact that a mathematical description of it is possible. He argued that as physics has progressed it has discarded models as an aid to explanation and discovery. Post-Galilean physics discarded the biological model of Aristotle, and modern physics has now discarded mechanical theories and models, being content to present its theories as pieces of mathematical formalism. Jeans put the matter this way: We cannot interpret the multidimensional configuration spaces of quantum physics as material space because material space has but three dimensions. Nor can we interpret the axioms of non-Euclidean geometry, especially the geometry of finite spaces, in terms of the congruences of material rods in material space. (This last claim is simply unwarranted.) Consequently, argued Jeans, the formalism of modern physical theory must be given a pure mathematical interpretation. (However, there is no sense in which we can speak of a pure mathematical interpretation, since "pure" here means "un interpreted.") Since the subject of pure mathematics is just thoughts, we may conclude, according to Jeans, that the stuff of the universe is mental. It is thought in the mind of God, the Pure Mathematician.

See also Aristotle; Cosmology; Geometry.


works by jeans

Eos; or Wider Aspects of Cosmogony. London: Kegan Paul, 1929.

The Universe around Us. Cambridge, U.K.: Cambridge University Press, 1929.

The Mysterious Universe. Cambridge, U.K.: Cambridge University Press, 1930.

The Stars in Their Courses. Cambridge, U.K.: Cambridge University Press, 1931.

New Background of Science. Cambridge, U.K.: Cambridge University Press, 1933.

Through Space and Time. Cambridge, U.K.: Cambridge University Press, 1934.

An Introduction to the Kinetic Theory of Gases. Cambridge, U.K.: Cambridge University Press, 1940.

Physics and Philosophy. Cambridge, U.K.: Cambridge University Press, 1942.

works on jeans

Milne, E. A. Sir James Jeans: A Biography. Cambridge, U.K.: Cambridge University Press, 1952.

Stebbing, Susan. Philosophy and the Physicists. London: Methuen, 1937. Ably criticizes Jeans's views.

G. C. Nerlich (1967)

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Jeans, James Hopwood (1877–1946)." Encyclopedia of Philosophy. . 24 Sep. 2018 <>.

"Jeans, James Hopwood (1877–1946)." Encyclopedia of Philosophy. . (September 24, 2018).

"Jeans, James Hopwood (1877–1946)." Encyclopedia of Philosophy. . Retrieved September 24, 2018 from

Learn more about citation styles

Citation styles gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

The Chicago Manual of Style

American Psychological Association

  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.